In a steam turbine, steam is expanded to generate rotational energy. The steam turbine has a plurality of stages, each stage having a guide blade ring with a plurality of guide blades and a rotor blade ring with a plurality of rotor blades. The rotor blades are fitted to the shaft of the steam turbine and rotate during operation of the steam turbine; the guide blades are fitted to the housing of the steam turbine and are stationary. When the steam turbine is in operation, the blades may be excited into vibration. The vibration is characterized in that a vibration node is arranged on the blade roots of the blades. The stress loading due to the vibration is high particularly at the blade roots, such that material fatigue may arise at the blade roots, making it necessary to exchange the guide blades, which is cost-intensive.
A flow duct, through which the steam flows when the steam turbine is in operation, is formed between in each case two guide blades arranged adjacent to one another. The velocity distribution of the flow downstream of the guide blade ring has, in the region of the trailing edges of the guide blades, local velocity minima which are termed wake depressions. The wake depressions may excite the rotor blades, arranged downstream of the guide blade ring, to vibrate.